V.I. Teleshevky, V.A. Sokolov

Development of non-contact methods of linear and angular dimensions measurement is a task of current importance. Optoelectronic measuring systems based on gas or semiconductor laser have great potential in solving this task. One of the fields requiring solution of this task is production of electrovacuum devices. Most parts of these devices have very high requirements of dimensional accuracy, surface roughness, durability and tightness of joints. A typical task of optical measurements is location of an object-s non-transparent edge in order to determine the accuracy of object-s spatial position, dimensions, form and surfaces positions. The laser beam acts as a non-contact optical jaw, same to caliper-s jaw. This article considers a fundamentally new method of optical jaw realization, performing phase or frequency conversion of object-s edge displacement. The method-s essence is placing the non-transparent edge in Fresnel diffraction zone of laser beam passing through acousto-optical modulator with ultrasonic wave running through it. As the beam diffracts the spectrum of scattered radiation forms a set of plant waves - diffraction lobes with different frequencies and directions. In the Fresnel zone lobes collide, forming complex running interference field with step equal or multiple to the acoustic wavelength. Moving the edge through Fresnel zone causes phase shift of photoelectrical measuring signal, which frequency is equal to the acoustic wavelength. Thus edge-s position is phase converted with high carrier frequency. Another way of the method-s resolution increase is edge-s position frequency conversion. The method-s essence is building the measuring system with acousto-optoelectronical positive feedback, that changes the converter-s behavoir. As a result the frequency of measuring signal is changed, and frequency shift is proportionate to measured position change. Thus mentioned above phase and frequency laser heterodyne measuring systems allow to measure edge-s displacement with 0.01 micron resolution with carrier frequency up to dozens of megahertz. The speed of non-contact measured objects can reach up to hundreds meters per minute